Femtosecond time-resolved coherent anti-Stokes Raman scattering for the simultaneous study of ultrafast ground and excited state dynamics: iodine vapour

Femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) is applied in order to investigate molecular dynamics in the gas phase. As model system iodine vapour is chosen. By changing the timing of the laser pulses of this non-degenerate four-wave mixing technique, the wavepacket motion on both the electronically excited and the ground states can be detected as oscillations in the coherent anti-Stokes signal. Different decay times are found for the amplitudes of the excited and ground-state beats. The results are compared with transients obtained from a conventional pump-probe technique, where laser-induced fluorescence is used for detection.